This invention relates to valve assemblies and valve stems, and in particular to valves the construction of which are optimized to reduce the sudden changes in pressure caused by routine mechanical opening and closing of the valves and which have a capability to allow detection of internal leakage therein.
In my U.S. Pat. No. 5,152,320, I disclosed diverter valves with pairs of shut-off valves arranged to both close in a direction opposite the fluid flow in order to prevent damage caused by xe2x80x9chammering.xe2x80x9d
This invention relates to alternative types of such diverter valves providing similar advantages with a simplified, economical construction. As in my above-noted patent, two valve plugs, actuated by a single actuator, each of which moves against the flow of the fluid to its closed position. The valve plugs are positioned on the valve stem shaft so that the valve seats are between the valve plugs. One of the valve plugs is removably attached to the shaft, such as by threaded fastening means, to allow for installation into and removal of the plugs from the valve body.
In a preferred embodiment the valve body comprises two substantially identical sections, an upper section and a lower section, each section having a side opening and an end opening, with a valve seat formed in the end opening. These two sections are oppositely arranged, with the end opening of each section facing the other section. The valve body also includes a T-shaped connecting section linked between the end openings of the two other sections. The connecting section has three openings, two of which are substantially co-linearly aligned and the third of which is non-aligned. The end opening of each of the first two sections is connected to one of the aligned openings of the T-shaped section.
Briefly, the invention relates to a valve stem assembly which includes a valve stem shaft connected a valve actuator having a pair of valve plugs removably attached to opposite ends of a shaft, the lowermost plug being supported on a hollow stem which forms an extension of the lower end of the shaft. The hollow stem permits any fluid leaking into a space between said shaft and the hollow stem to escape, thus providing externally visible evidence of any such leakage. Preferably the second valve plug body is attached to the shaft by threads, and an O-ring seal is provided between a shoulder on the shaft and the valve plug body.
Other objects and advantages of the invention will become apparent hereinafter.